1. Technical Field
The present disclosure relates to electrically isolating a patient from medical equipment, and more particularly, to electrically isolating a patient ground from a ground of an electrosurgical generator.
2. Background of Related Art
Patients undergoing medical procedures are generally electrically isolated from stray electrical energy of medical equipment connected to the patient. For non-interventional procedures (no medical devices are inserted into the subject), isolation of the patient from the medical device is accomplished by incorporating insulating materials in the construction of surfaces that the patient is likely to touch (e.g. surface coils, patient bed, etc.).
For interventional procedures (medical devices are inserted into the subject), the issue of patient isolation is more complicated since interventional devices themselves are in contact with the patient. This can be especially critical if the invasive device is in contact with electrically-sensitive tissue (e.g., cardiac muscle, brain tissue, etc.). Due to the nature of microwave energy delivery for therapeutic procedures, special requirements exist in isolating a patient, such as the construction of an isolation circuit for use with a microwave generator.
The issue of isolating a patient ground from a generator's ground (i.e., Earth ground) is complex in microwave generators having frequencies above about 500 MHz. In generators with lower frequencies, a transformer may be used to isolate the patient from the generator's ground. As the frequencies get higher, the core loss of the transformer and parasitic elements often overwhelm attempts to transfer energy across an isolation boundary.
Another method of isolating a patient ground from a generator's ground may be with the use of a capacitor. However, with microwave frequencies, the capacitors will add their own losses in terms of reflections and parasitic losses due in part to the voltage isolation requirements of the capacitor.
Accordingly, a need exists for improved devices and methods of isolating a patient ground from a ground of an electrosurgical generator.